Hitherto, an acoustic echo canceller has been used as a device for removing an echo component routed from a loudspeaker to a microphone (for example, refer to Non-patent Document 1). The acoustic echo canceller estimates a transmission function of an acoustic transmission system from a loudspeaker to a microphone, thereby estimating an echo component and removing it from a sound collection signal.
Non-patent Document 1: “Acoustic systems and digital technology” edited by Juro OHGA, Yoshio YAMASAKI, and Yutaka KANEDA, the Institute of Electronics, Information and Communication Engineers, 1995, pp. 210-211